The invention relates to a control apparatus in accordance with the preamble of the main claim. In a known control apparatus of this kind, in order to maintain a very precise ratio of air to fuel in an auto-igniting internal combustion engine, the recirculated exhaust gas quantity is controlled in a very expensive manner in that the recirculated exhaust gas quantity, after precise apportionment of the air quantity in relationship to the injected fuel quantity, comprises the remnant charge of the combustion chambers of the engine.
An exhaust gas recirculation valve control apparatus is also known in which the control pressure for the pneumatic adjustment device of the exhaust gas recirculation valve is a mixture of the pressure prevailing in the Venturi restriction of a carburetor and the pressure prevailing downstream of the throttle valve of the carburetor. This apparatus thus makes use of a known carburetor and is thus restricted to use in externally ignited internal combustion engines. The control pressure can be modified by means of throttles in the lines leading off from the pressure withdrawal points in such a manner that the recirculated quantity of exhaust gas corresponds approximately to particular requirements of the engine at various operational points.
Another new apparatus for setting a desired exhaust gas recirculation rate in accordance with the air quantity induced by the carburetor has a slit-like cross section in the pivoting range of the throttle valve, which cross section is also partially opened toward the intake manifold upstream of the throttle valve when the throttle valve is closed. In accordance with the extent to which the throttle valve is opened, a control pressure is attained in the work chamber of a pneumatically functioning exhaust gas recirculation valve which communicates with the slit-like cross section which pressure varies in accordance with the extent of the throttle valve opening and with the underpressure prevailing downstream of the throttle valve. In order to obtain proper proportions of recirculated exhaust gas, the cross section of the slit-like opening can be appropriately controlled. This apparatus as well relates to exhaust gas recirculation in externally ignited internal combustion engines and in particular engines which are supplied with operational mixture by carburetors.